Study Of Single-Step Decolorization And Defluorinate Technology Of Wet-Process Phosphoric Acid

The decolorization and defluorinate of wet-process phosphoric acid isimportant production process of the phosphoric acid enterprise, and raw materialthe wet-process phosphoric acid must be carried on decolorization anddefluorinate in order to obtain the high quality phosphoric acid or the phosphate.To explores a technology of decolorization and defluorinate of wet-processphosphoric acid with higher efficiency, lower consumption, operation easily andfewer investment of equipments, it will have a good impetus function to thewet-process phosphoric acid production in the future, and have a positivecontribution of human life.In this study, it is decolorizationed and defluorinated of wet-processphosphoric acid by the powdery active carbon and the sodium carbonate,reactions and sedimentations under condition of water bath and agitation, thepurified wet-process phosphoric acid is filtrated by Gore membrane insteaded ofnormally used filtration cloth. Through the orthogonal experiment, the effectabilities of six factors were studied; through single factor experiment, the effectlaws of reaction temperature, reaction time, dosage of active carbon, dosage ofNa₂CO₃, sedimentation time and type of active carbon were determined aboutthe decolorization and defluorinate.These following conclusions were drawn on the basis of the experiments:(1) It is feasible to use active carbon and Na₂CO₃ to single-stepdecolorization and defluorinate of wet-process phosphoric acid. In this method,the decolorization rate can reaches 90% and the defluorinate rate can reaches80% on the best technical conditions of the effect laws of reaction temperature,reaction time, dosage of active carbon, dosage of Na₂CO₃, sedimentation time and type of active carbon.(2) The active carbon have not only quite good affect of decolorization, butalso have quite good affect of defluorination, and have orthogonal interactionwith the defluorinate.(3) Considering the practical production, and the powdery active carbonand Na₂CO₃ were used to the composition of decolorization and defluorinate, thebest technical conditions are: reaction temperature 70℃, reaction time 90min,dosage of active carbon 0.3%, dosage of Na₂CO₃ 2% and sedimentation time 1day. At the condition, the phosphoric acid is clear and transparent, thechromaticity is close to the hot-process phosphoric acid, and quantity offluorine decline to 0.03mg/ml.(4) The phosphoric acid damage rate about 6% in the method of single-stepdecolorization and defluorinate of wet-process phosphoric acid.(5) The technology has some characteristics of higher efficiency, lowerdamage rate of energy, operation easily and fewer investment of equipments, itis fit to deeply processing by small and medium-sized enterprises.(6) It is feasible to use the spectrophotometer determination phosphoricacid' chromaticity, it has more intuitionist to reflect the change rule ofchromaticity and the result of quantity compare than the original visualcorrelation method, and have characteristics of operation easily and expressintuitively.